The application discloses an LED display device and a driving method thereof. The LED display device comprises a plurality of LEDs serving as pixel units. The method includes: gray scale data are generated according to a display image; according to a practical frame rate and a practical refreshing rate, a practical gamma table is generated; on the basis of the practical refreshing rate, gamma correction is carried out on the gray scale data to obtain display data; a PWM signal is generated based on the display data; and a constant-current source is controlled to provide a driving current by using a PWM signal, so that LEDs are lightened to generate brightens corresponding to a gray scale. According to the method, the practical gamma curve is generated based on the practical frame rate and the practical refreshing rate, thereby improving an effect of gamma correction.